But US authorities want more tests as women in trials say the drug makes them sleepy

A DRUG designed to treat "distressing low desire in women " - in effect, Viagra for females – is a step closer to reality, according to a small American company, Sprout Pharmaceuticals, based in North Carolina.

The US Food and Drug Administration, which strictly controls permissions for new pharmaceuticals, has asked for more trials to determine how the drug, flibanserin, interacts with other medicines and, in particular, how it affects driving ability.

That's because nearly ten per cent of woman who have taken the daily pill in company trials have reported sleepiness – which, given its intended purpose, is hardly ideal.

Some media reports have interpreted the FDA's demand for more data as a negative. But the husband-and-wife team who run Sprout Pharmaceuticals, Robert and Cindy Whitehead, believe it's a positive because the FDA is asking for only a relatively small trial, involving 25 to 50 patients, after which Sprout plans to resubmit its application later this year. Cindy Whitehead described the FDA request as "a significant step toward the approval of flibanserin".

Flibanserin is a non-hormonal drug which acts on brain chemicals that affect appetite and mood. If it does get the green light, it will have been a long time coming.

While Viagra (chemical name: sildenafil) went from patent to FDA approval (in 1998) in two short years, it's been more than a decade since flibanserin was first patented for the treatment of "hypoactive sexual desire disorder" - or a lack of sexual appetite deemed serious enough to cause emotional distress.

Big Pharma – corporations like Pfizer (the Viagra people) and Procter & Gamble – have mainly given up trying to bring such a drug to market. Sprout Pharmaceuticals, very much a Small Pharma outfit, acquired flibanserin in 2011 from the German giant Boehringer Ingelheim who gave up because too women taking part in its trials reported only "a modest uptick in sexually satisfying events", as Associated Press puts it.

If the FDA does eventually accept it, there's still the medical profession to win over - which won't be easy. Because so many other factors affect a woman's desire, doctors would first have to rule out relationship problems, hormone disorders, depression and, last but not least, whether another medication could be affecting the patient's mood. She might, for instance, have taken a headache pill – because she really does have one.